Self-Mode-Locking Investigation of High-Power Optically Pumped Semiconductor Laser

Advisor: Yung Fu Chen

Student: Yi Chun Lee

Date: 2010/07/09

Solid-State Laser Physics Lab.

NCTU Electrophysics

Y.C. Lee

高功率光激發式半導體雷射之自鎖模研究

Outline1. Introduction 1.1 Background and Motivation

1.2 OPSL V.S DPSSL

1.3 OPSL Technology

2. OPSL Experimental Results 2.1 OPSL Parameter Optimized

2.2 Spontaneous Mode-Locking of OPSL

2.3 Theoretical Simulation

3. Summary and Future Work

NCTU Electrophysics

Solid-State Laser Physics Lab. Y.C. Lee

• Flashlamp Pumped Double Frequency Nd:YAG Laser ~532nm

• Flashlamp Pumped Nd:YAG Laser ~1064nm

• Diode Pumped Double Frequency Nd:YVO4 Laser ~532nm

• Diode Pumped Double Frequency Nd:YAG Laser ~561nm

• Optical Pumped Semiconductor Laser ~577nm

• Diode Laser ~810nm

閉角型青光眼之小梁成型術

視網膜剝離、眼底止血

青光眼治療、眼底光凝結手術

白內障手術眼底黃斑部病變

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Solid-State Laser Physics Lab. Y.C. Lee

Applications for OPSL

• Medical Field• Life Science and Research• Forensics• Graphic Arts and Display

Optically Pumped Semiconductor Laser

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Solid-State Laser Physics Lab. Y.C. Lee

60fs

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Solid-State Laser Physics Lab. Y.C. Lee

Polarizer

Cr4+

Crystal

Output Coupler

Flash Lamp

1064 nm

Reflector Mirror

Reflector

Reflector

Nd:YAG Rod

2 ns/div

Flash lamp pumped passively Q-switched Nd:YAG laser

Strange Phenomenon in Time DomainStrange Phenomenon in Time DomainNCTU

Electrophysics

Solid-State Laser Physics Lab. Y.C. Lee

Tr

Fiber-coupled LD @976 nm

HR @ 1030~1100 nm

FP filter

HT@976 nmHR@1030~1100 nm

Laser output

Yb doped double-clad fiber PM; clad/core: Dia. 250/30 μm (3m) NA >0.46 /<0.06

cavity

R~4%

3x50 QWs

Diode pumped passively Q-switched Yb-doped fiber laser

10 ns/div

Strange Phenomenon in Time DomainStrange Phenomenon in Time DomainNCTU

Electrophysics

Solid-State Laser Physics Lab. Y.C. Lee

Tr

100 ns/div 1 ns/div 2 ns/divTr Tr

Cw-pumped diffusion-bonded Nd:YVO4 laser

Cavity length ： 19 cm

Cavity length ： 45 cm

Nd:YVO4 Crystal

Output Coupler

Coupling Lens

Diode Pumped Diffusion-Bonded Nd:YVO4 LaserDiode Pumped Diffusion-Bonded Nd:YVO4 Laser808nm Laser Diode

Strange Phenomenon in Time DomainStrange Phenomenon in Time DomainNCTU

Electrophysics

Solid-State Laser Physics Lab. Y.C. Lee

1064nm

Self-Mode-Locked Nd:YVO4 Laser Self-Mode-Locked Nd:YVO4 Laser

200 ps/div

Stable CW mode locking and short pulse width

Wavelength (nm)

1064.2 1064.3 1064.4 1064.5 1064.6

Inte

nsit

y (a

.u.)

0

2

4

6

8

10

12

Delay time (ps)

0 20 40 60 80 100 120 140

Inte

nsity

(a.

u.)

0

50

100

150

200

500 ns/div(a)

(b) 500 ps/div

(c) pulse width ~ 23 ps

39 ps

(d)

Wavelength (nm)

1064.2 1064.3 1064.4 1064.5 1064.6

Inte

nsit

y (a

.u.)

0

2

4

6

8

10

12

Delay time (ps)

0 20 40 60 80 100 120 140

Inte

nsity

(a.

u.)

0

50

100

150

200

500 ns/div(a) 500 ns/div(a)

(b) 500 ps/div(b) 500 ps/div

(c) pulse width ~ 23 ps

39 ps

(d)

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Solid-State Laser Physics Lab. Y.C. Lee

Output coupler

Fiber coupled LD

DPSSL – Diode Pumped Solid State Laser 二極體激發式固態雷射 OPSL – Optically Pumped Semiconductor Laser 光激發式半導體雷射

In 1980s, the progress in the growth technology of semiconductor

heterostructures developed the high-power diode laser pumped

with a solid gain medium is so called diode-pumped solid-state

(DPSS) lasers.

In 1997, M. Kuznetsov, F.Hakimi and A. Mooradian demonstrated

the first optically-pumped semiconductor laser (OPSL).

OPSL V.S DPSSL

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Solid-State Laser Physics Lab. Y.C. Lee

△Ec

△Ev

Eg Eg well

barrier

The Mechanism of Stimulated Emission - Four-Level System in Solid-State Laser and Semiconductor Laser

OPSL V.S DPSSL

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Solid-State Laser Physics Lab.

Y.C. Lee

OPSL

Optically Pumped Semiconductor Laser

Diode Pumped Solid State Laser

DPSSLV.S

OPSL V.S DPSSL

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Solid-State Laser Physics Lab.

Y.C. Lee

• Semiconductor as Gain Medium - Substrate - Quantum Well - Bragg Mirror

OPSL Technology

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Solid-State Laser Physics Lab. Y.C. Lee

GaAs substrate based

InP substrate based

AlGaAs (800-870nm)

InGaAs (870-1150nm)

GaInNAs (1.1-1.5μm)

Wavelength ＞ 1.3μm

OPSL Technology

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Solid-State Laser Physics Lab. Y.C. Lee

SubstrateMulti-layer mirrors (DBRs)

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

Laser optical standing wave

Surface barrier

Cap layer

Pumping absorbing region

λ /2

Quantum wells

Ene

rgy

Semiconductor air

SubstrateMulti-layer mirrors (DBRs)

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

Laser optical standing wave

Surface barrier

Cap layer

Pumping absorbing region

λ /2

Quantum wells

Ene

rgy

Semiconductor air

Fig4.1.2 Bandgap diagram and operation principle of the OP-VECSEL

SubstrateMulti-layer mirrors (DBRs)

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

Laser optical standing wave

Surface barrier

Cap layer

Pumping absorbing region

λ /2

Quantum wells

Ene

rgy

Semiconductor air

SubstrateMulti-layer mirrors (DBRs)

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

1 0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.52.5

0.5

1 sin x( ) 2

101 x

Laser optical standing wave

Surface barrier

Cap layer

Pumping absorbing region

λ /2

Quantum wells

Ene

rgy

Semiconductor air

Fig4.1.2 Bandgap diagram and operation principle of the OP-VECSEL

Substrate

Active region

Cap layer

x

…..

…..

30 periods

2

• The Length of Quantum Well would be designed as 1/2 laser wavelength

• Laser Wavelength would slightly shifted according to quantum well design.

OPSL Technology

NCTU Electrophysics

Solid-State Laser Physics Lab. Y.C. Lee

Outline1. Introduction 1.1 Background and Motivation

1.2 OPSL V.S DPSSL

1.3 OPSL Technology

2. OPSL Experimental Results 2.1 OPSL Parameter Optimized

2.2 Spontaneous Mode-Locking of OPSL

2.3 Theoretical Simulation

3. Summary and Future Work

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Solid-State Laser Physics Lab. Y.C. Lee

Cavity Length

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Solid-State Laser Physics Lab.

OPSL Optimized

Pumping Source

Semiconductor Gain Medium

Y.C. Lee

1060 nm

OPSL Optimized

OPSL Optimized by using

• Different Radius of Output Coupler

• Cavity Length

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Solid-State Laser Physics Lab. Y.C. Lee

Focusing lens

Semiconductor Gain Medium Output

Coupler

Laser Diode

1060 nm

High speed photo-detector

Pumped Current (A)

10 15 20 25 30

Ave

rage

Out

put P

ower

(W

)

0

2

4

6

8

Cavity Length 30mm

Cavity Length 50mm

Pumped Current (A)

12 14 16 18 20 22 24 26 28 30

Ave

rage

Out

put P

ower

(W

)

0

2

4

6

8

10

Cavity Length 25 mmCavity Length 50 mmCavity Length 100 mm

Pumped Current (A)

12 14 16 18 20 22 24 26 28 30

Ave

rage

Out

put P

ower

(W

)

0

2

4

6

8

Cavity Length 50 mmCavity Length 25 mm

ROC = 50mmCavity Length = 30mm, Max Power ~7.4WCavity Length ~ 50mm, Max Power ~7.03W

ROC = 250mmCavity Length = 25mm, Max Power ~7.8WCavity Length = 50mm, Max Power ~8.0WCavity Length = 100mm, Max Power ~ 7.8WROC = 2000mm

Cavity Length = 25mm, Max Power ~6.8WCavity Length = 50mm, Max Power ~6.7W

ROC = 250mmCavity Length = 50mm, Max Power ~8.0W

• Different Radius of OC and Cavity Length.OPSL Optimized

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Solid-State Laser Physics Lab.

Spontaneous Mode-Locking of OPSL

Mode-Lock Optimized

5ns/div

Power Optimized

5ns/div

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Focusing lens

Semiconductor Gain Medium Output

Coupler

Laser Diode

1060 nm

Digital oscilloscope

High speed photo-detector

Spontaneous Mode-Locking of OPSL

Pump power (W)

4 6 8 10 12 14 16 18 20 22

Ave

rage

Out

put P

ower

(W

)

0

2

4

6

8

IP Curve of Mode Locking for 25cm Cavity LengthIP Curve of Power Optimized for 25cm Cavity Length

Wavelength (nm)

1058 1059 1060 1061 1062 1063 1064

Inte

nsit

y (a

.u.)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4Specturm of Mode-Locking Spectrum of Power Optimized

ROC = 250mmCavity Length ~ 250mm

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5ns/div5ns/div

Power Optimized Mode-Lock Optimized

Spontaneous Mode-Locking of OPSL

ROC = 250mmCavity Length ~ 250mm

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Solid-State Laser Physics Lab. Y.C. Lee

Spontaneous Mode-Locking of OPSL

ROC = 250mmCavity Length = 187mm

Pump power (W)

4 6 8 10 12 14 16 18 20 22

Ave

rage

Out

put P

ower

(W

)

0

2

4

6

8

IP Curve of Mode Lock Optimized for 18.75cm(3:1) Cavity LengthIP Curve of PowerOptimized for 18.75cm(3:1) Cavity Length

Wavelength (nm)

1058 1059 1060 1061 1062 1063 1064

Inte

nsity

(a.

u.)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4Specturm of Mode-Locking Spectrum of Power Optimized

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5ns/div5ns/div

Power Optimized Mode-Lock Optimized

Spontaneous Mode-Locking of OPSL

ROC = 250mmCavity Length = 187mm

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Solid-State Laser Physics Lab. Y.C. Lee

Spontaneous Mode-Locking of OPSL

Pump Power (W)

4 6 8 10 12 14 16 18 20 22

Ave

rage

Out

put P

ower

(W

)

0

1

2

3

4

5

6

7

IP Curve of Mode Lock Optimized for 12.5cm(4:1) Cavity LengthIP Curve of Power Optimized for 12.5cm(4:1) Cavity Length

ROC = 250mmCavity Length = 125mm

Wavelength (nm)

1058 1059 1060 1061 1062 1063 1064

Inte

nsit

y (a

.u.)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4Spectrum of Mode-Locking Spectrum of Power Optimized

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2ns/div

Power Optimized Mode-Lock Optimized

Spontaneous Mode-Locking of OPSL

ROC = 250mmCavity Length = 125mm

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Solid-State Laser Physics Lab. Y.C. Lee

2ns/div

Spontaneous Mode-Locking of OPSL

ROC = 250mmCavity Length = 86mm

Pump power (W)

4 6 8 10 12 14 16 18 20 22

Ave

rage

Out

put P

ower

(W

)

0

1

2

3

4

5

6

7

IP Curve of Mode Lock Optimized for 8.6cm(5:1) Cavity LengthIP Curve of Power Optimized for 8.6cm(5:1) Cavity Length

Wavelength (nm)

1058 1059 1060 1061 1062 1063 1064

Inte

nsity

(a.

u.)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4Specturm of Mode-Locking Spectrum of Power Optimized

NCTU Electrophysics

2ns/div2ns/div

Power Optimized Mode-Lock Optimized

Spontaneous Mode-Locking of OPSL

ROC = 250mmCavity Length = 86mm

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Solid-State Laser Physics Lab. Y.C. Lee

Pump Power (W)

4 6 8 10 12 14 16 18 20 22

Ave

rage

Out

put P

ower

(W

)

0

1

2

3

4

5

6

7Mode Lock Optimized for 12.5cm(4:1) Cavity LengthPower Optimized for 12.5cm(4:1) Cavity LengthFundamental Mode for 12.5cm(4:1) Cavity Length

Spontaneous Mode-Locking of OPSL

ROC = 250mmCavity Length = 125mm

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Power Optimized

2ns/div

2ns/div

Mode-Lock Optimized

2ns/div

Fundamental Mode

Solid-State Laser Physics Lab.

Spontaneous Mode-Locking of OPSL

• Scan the Beating to determine the distribution of high-order mode.

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Solid-State Laser Physics Lab. Y.C. Lee

Focusing lens

Semiconductor Gain Medium Output

Coupler

Laser Diode

1060 nm

Digital oscilloscope

High speed photo-detector

1 2 3 4 5 6 7

8

9

10

11

2ns/div1

2ns/div8

2ns/div4

2ns/div7

2ns/div62ns/div11

2ns/div3

Y.C. Lee

1.6 3.2 4.8. 6.4. 8.0.

-75

-35

-45

-55

-65

Frequency (GHz)

Spec

tral

pow

er d

ensi

ty

(dB

m)

Spontaneous Mode-Locking of OPSL

Longitudinal Frequency

Transverse Frequency

11 21

TR

cos g gf

T

1ii

Lg

R

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Solid-State Laser Physics Lab. Y.C. Lee

Fundamental Mode

High-Order Mode

1 4 7

8

11

Detected Point

3 6

High-Order Mode

Spontaneous Mode-Locking of OPSL

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Solid-State Laser Physics Lab. Y.C. Lee

R

lnmqq

lck cav

cav

nmqnmq 1cos

1)( 1

0,,

,,

q 0 表示縱向模態的指標， lcav 代表有效的共振腔長， R 為曲率半徑。

Rnmq

nmq z

znmi

ctzikzR

yxik

nmz

yx

nmnmq eeez

yH

z

xHe

znmtzyxE

1

,,

22

,,2

22

tan)1()()(2

)(

)(

)(

0,, )(

2

)(

2

)(! !2

1),,,(

1

0,,, ),,,(),,,(

M

qnmq

Mnm tzyxEtzyxE

NCTU Electrophysics

Solid-State Laser Physics Lab. Y.C. Lee

Theoretical Simulation

NCTU Electrophysics

Solid-State Laser Physics Lab.

),,,(10

3),,,(

2

1),,,(),,,( 0,11,00,0, tzyxEtzyxEtzyxEtzyxE MMMM

nm

Y.C. Lee

Theoretical Simulation

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Solid-State Laser Physics Lab. Y.C. Lee

Theoretical Simulation

2ns/div1

2ns/div3 3 2ns/div

2ns/div1

2ns/div22 2ns/div

NCTU Electrophysics

Solid-State Laser Physics Lab.

Experimental Results Theoretical Simulation

Y.C. Lee

2ns/div7 2ns/div7

2ns/div62ns/div6

5 2ns/div

NCTU Electrophysics

Solid-State Laser Physics Lab.

2ns/div4 2ns/div4

Y.C. Lee

5 2ns/div

9 2ns/div9 2ns/div

10 2ns/div10 2ns/div

2ns/div11 11 2ns/div

NCTU Electrophysics

Solid-State Laser Physics Lab.

2ns/div8 8 2ns/div

Y.C. Lee

1 2 3 4 5 6 7

8

9

10

11

2ns/div1

2ns/div8

2ns/div4

2ns/div7

2ns/div62ns/div11

2ns/div3

2ns/div1

2ns/div73 2ns/div

11 2ns/div 2ns/div6

2ns/div4

8 2ns/div

Y.C. Lee

Outline1. Introduction 1.1 Background and Motivation

1.2 OPSL V.S DPSSL

1.3 OPSL Technology

2. OPSL Experimental Results 2.1 OPSL Parameter Optimized

2.2 Spontaneous Mode-Locking of OPSL

2.3 Theoretical Simulation

3. Summary and Future Work

NCTU Electrophysics

Solid-State Laser Physics Lab. Y.C. Lee

Summary

OPSL also discovered the spontaneous mode-locking phenomenon.

The beating of the mode-locking output pulse trains are observed of transverse modes coupling.

Theoretical simulation is matched to experimental results.5ns/div 5ns/div

NCTU Electrophysics

Solid-State Laser Physics Lab. Y.C. Lee

0/1 1/1

1/2

2/31/3

1/4 3/42/5 3/5

1/5 2/7 3/8 3/7 4/7 5/8 5/7 4/6

1/6 2/9 3/11 3/10 4/11 5/13 5/12 4/9

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Solid-State Laser Physics Lab.

Farey Tree

Y.C. Lee

Future Work

1:3

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Future Work

Y.C. Lee

1:4

2ns/div

NCTU Electrophysics

Solid-State Laser Physics Lab.

Future Work

Y.C. Lee

2:5

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Solid-State Laser Physics Lab.

Future Work

Y.C. Lee

5:12

NCTU Electrophysics

Solid-State Laser Physics Lab.

Future Work

Y.C. Lee

5ns/div

7:17

12:29

NCTU Electrophysics

Solid-State Laser Physics Lab.

Future Work

Y.C. Lee

Focusing lens

Semiconductor Gain Medium Output

Coupler

Laser Diode

1060 nm

Digital oscilloscope

High speed photo-detector

SESAM

Future Work

NCTU Electrophysics

Solid-State Laser Physics Lab. Y.C. Lee

Thanks for your attention!

NCTU Electrophysics

Solid-State Laser Physics Lab. Y.C. Lee